1. Field of the Invention
The present invention relates generally to a speed indicator, and more particularly to a speed indicator adapted for use in bicycle speed control apparatuses which control the shifting devices.
2. Description of the Prior Art
Mounting a speed control apparatus on the handlebars of a bicycle for controlling the shifting actions of the bicycle is a known art. As the use of the speed control apparatus in shifting the winding member does not allow the cyclist to exactly know the control situation, there are some inventions which disclose mounting of a speed indicator on the speed control apparatus to indicate the speed of the bicycle.
One such speed indicator is described in U.S. Pat. No. 5,012,692 to Nagano. In FIG. 8 of said patent, a speed indicator resembling a ring is illustrated, but it is not described in detail in the disclosure. In U.S. Pat. No. 5,325,735, also issued to Nagano, a shifting device with a takeup reel is disclosed. A disc-like speed indicator of the shifting device connected to a crown gear is disposed on the takeup reel, and the crown gear is caused to engage with a coaxial gear so that the disc-like speed indicator is driven via a tension pulley. Such a speed indicator as taught in U.S. Pat. No. 5,325,735 is complicated in construction. And besides, as a pointer is used to indicate the numerical signs, misreading may easily occur.
There is another problem with the conventional shifting devices mounted on the handlebars of bicycles. In the conventional shifting device consisting of a speed control cable wound around the takeup reel, since the diameter of each gear does not increase in a uniformly gradual manner, when the speed control cable is wound by the takeup reel, the distance displaced by the shifting lever between any two adjacent shifts is not uniform, hence the distance between any two adjacent shifts indicated by the speed indicator will also vary. For instance, supposing the distance displaced by the speed indicator from the first shift sign to the second shift sign is 5 mm, then the distance displaced by the speed indicator from the second shift sign to the third shift sign may be 6 mm, and that from the third shift sign to the fourth shift sign may be 7.2 mm. The speed thus indicated by the speed indicator is not precise. Solution to this problem is therefore necessary.